DESCRIPTION: There are conflicting data regarding the associations between serum levels of OCCs (e.g., DDE) and of PCB with the risk of developing breast cancer. The application is intended to complete a previously-supported, case-control study to determine whether the levels of these substances is elevated in the serum and adipose tissue of breast cancer cases, diagnosed on Long Island, compared to controls from the same location (benign breast disease and surgical controls). To date, 338 case patients, 418 women with benign breast disease and 197 surgical controls have been interviewed, and 819 adipose samples and 896 serum aliquots collected. One fourth of these samples have been analyzed and the preliminary results show that DDE and possibly certain PCB congeners are associated with increased risk of breast cancer. The future plan is to continue in order to: 1) complete assays on the remaining 3/4 of the samples; 2) determine the lipid-adjusted serum concentrations of OCCs and their partition between serum and adipose tissue; 3) correlate OCC levels with age, body mass, and location in order to adjust breast cancer risk for these confounders; 4) determine whether adjusted risk estimates differ by estrogen receptor status of the tumors; 5) correlate OCC levels with recurrence and mortality from breast cancer via follow-up cases; 6) study short term (1-3 yr.) stability of serum OCC and PCB levels and the impact of treatment on these levels; 7) estimate breast cancer risk, utilizing different classifications for PCB congeners; and 8) determine whether OCC-related risk of breast cancer can be correlated with degrees of atypia of the benign breast biopsy controls, using pathologic reviews of samples from over 400 patients.